Physiology - Respiratory Flashcards
The function of the respiratory system
- Gas exchange (02 added to blood from air. C02 removed from blood to air) 2. Acid base balance - pH 3. Protect from infection 4. Communicating via speech
Why do we need to breathe? Why is gas exchange so important
To produce energy
Energy is
Fundamental in all living systems
What does 02 relate to energy in living systems
Burning oxygen produce carbon dioxide Respiratory system responsible for 02 in and c02 out
What 2 systems does gas exchange link?
Respiratory system and cardiovascular system
What biochemical process releases energy from glucose either via glycolysis or oxidative phosphorylation.
Cellular/internal respiration
What is cellular/internal respiration?
biochemical process releases energy from glucose either via glycolysis or oxidative phosphorylation.
What is the movement of gases between air and body cells via both resp and CVS
External respiration
What is external respiration
the movement of gases between air and body cells via both resp and cvs
Which produces more energy (ATP) Glycolysis or oxidative phosphorylation
oxidative phosphorylation
we cannot survive on glycolysis alone
explain the pulmonary circulation compared to systemic circulation
pulmonary circulation is opposite systemic circulation in function and terminology
Pulmonary circulation delivers Co2 to lunch and collects 02 from lungs.
Systemic circulation delivers 02 to peripheral tissue and collects co2
Pulmonary circulation _______ (delivers/collects o2 co2)
Pulmonary circulation delivers Co2 to lung and collects 02 from the lungs.
Systemic circulation ________ (delivers/collects o2 co2)
Systemic circulation delivers 02 to peripheral tissue and collects co2
Pulmonary ___ carries ____ blood
Pulmonary ___ carries ___ blood
Pulmonary arteries carry deoxygenated blood
Pulmonary veins carry oxygenated blood
upper respiratory system
Nose - enters the body through the nose (more effective than the mouth) where cilia and mucus trap and warm moisten the air.
Pharynx - from nose air moves down the pharynx or throat, which is shared with the digestive system
Epiglottis - this small flap of tissue folds over the trachea and prevents food from entering it when you swallow.
Larynx - the voice box, contains vocal chords that vibrate to produce sounds
Lower respiratory tract system
Trachea - from the pharynx air moves down toward the lungs through the trachea. made up of stiff rings of cartilage that support and protect it. travels down to sternal angle (splits for 2 primary bronchi)
Bronchus - Air moves from the trachea into the right and left bronchi, which lead inside the lungs
Lung - The main organs of respiration - soft, spongey texture is due to the many thousands of tiny hollow sacs that compose them
where does gas exchange occur?
Alveoli (little sacs in lunchs)
How many fissures in the right lung?
two fissures in the right lung split the lung into three lobes.
horizontal fissure and oblique fissure.
which fissure splits the superior lobe from the middle lobe
horizontal fissure
the horizontal fissure splits which lobes?
superior lobe of the right lung to the middle lobe.
the oblique fissures split
Right lung - middle lobe from inferior lobe
left lung - superior lobe and inferior lobe
which fissure splits superior and inferior lobes and which lung
Left lung - oblique
how many fissured on left lung?
one - oblique fissure
What cavity is inside the thoracic cavity?
The pleural cavity
Define the thoracic cavity
Defined by the ribs within the inferior border being the diaphragm and pleural cavity is a cavity within the thoracic cavity.
The trachea branches at what level?
Sternal angle
each bronchus branches __ times
22 times
Bronchopulmonary segments
as well as lobes lung tissues are broken into tertiary segments and one tertiary bronchi going to each segment of the lung
the semi ridgid tubed of the airway are maintained by
c shaped rings of cartilage
why do the upper airways, trachea and bronchi have c shaped rings of cartilage
to maintain patency of airway - give degree of rigidity that stops them collapsing or getting compressed.
how many of generations of branchine between the trachea and alveoli
24 generations
where do the cartilaginous rings stop down the airway?
beyond the bronchi - into bronchioles and smaller
what holds the airways open if the cartilaginous rings are not present
patency is maintained by the physical forces that act on the lungs.
where is dead space - how much dead space is there.
bronchi, bronchioles, and trachea as they are too thick-walled for gas exchanged. There is roughly 150 milliliters of air sitting in dead space
which bronchi are wider and more verticle - why is this significant?
The right bronchi is wider and more vertical - aspirated foreign bodies are more likely to get stuck in the right bronchi
where is the most air resistance to the airflow?
why?
from the trachea to smaller bronchi
The cross-sectional area is larger in bronchioles and alveoli (because they have more divisions all around - each small air way has many generations and openings where trachea e.g. has only one large opening)
what does bronchodilation do to resistance in lungs
dilates the airways - lowers resistance.
where is the “conduction zone?”
Trachea
primary bronchi
smaller bronchi
bronchioles
Where is the respiratory zone
alveoli
what does air in the conducting zone do?
Sits in “dead space”
airway diameter and resistance can be altered by
the activity of bronchial smooth muscle
contraction decreases diameter = increases resistance
relaxation increases diameter = decreases resistance
sympathetic acts on bronchial smooth muscle
which receptors
the sympathetic nervous system acts on beta two receptors (two lungs) cause bronchial smooth muscle relaxation.
sympathetic acts on bronchial smooth muscle what happens, what transmitters on what receptor
when adrenaline and noradrenaline bind to beta two receptors in the lungs it causes relaxation smooth muscle then increases the diameter of airway = reduces resistance
In sympathetic response, why do re want this reaction to our lungs?
increase dilation and reduced resistance means more ventilation
increased 02 delivery to our muscles means more energy so they can function more efficiently so we can fight or flight (run)
airway to the alveoli - gas exchange to which system
this is where exchange can take place in direct contact with tthe only part of the cardiovascular system. (cardiovascular tree)
what CVS bed is surrounding the area of gas exchange in respiratory system
capillary bed (network of capillaries) are surrounding the alveoli
what does the CVS bed (attached to the area of gas exchange in respiratory) then join on to, to continue the CVS circulation
Pulmonary artery - which carries deoxygenated blood back from the systemic venous circulation coming from the right side of the heart to the lungs.
carrying blood full of co2
Once the blood is oxygenated in the cvs bed surrounding the alveoli ____
through the ______
flows out of the capillary bed to the left side of the heart through the pulmonary vein
what are elastic fibres for that surround alveoli
they expand during inspiration and released expiration to squeeze alveoli and force air out of the respiratory system. (expiration at rest is passive)
expiration at rest is__
passive
alveoli components
one type of cell makes a bulk alveolar wall.
studded with type 2 cells which release surfactent
which type of cells do gas exchange and which do not
type1 cell makes a bulk alveolar wall - gas exchange
studded with type 2 cells which release surfactant NOT FOR gas exchange
which alveoli cell does not do gas exchange, what does it release.
studded with type 2 cells which release surfactent
which WBC are around the respiratory system
macrophages - important for immunity
why are there WBC dotted on the respiratory system?
The respiratory system is one of the points in the body where the external environment and internal environment meet. - important to have lots of immune tissue
emphysemia does what to surface area for gas exchange?
emphysema results from the destruction of alveoli in a way we lose surface area available for gas exchange
This decrease impacts resp function. Gas exchange between lungs and blood is only possible at alveoli due to thin surface.
Airway resistance determines___
how much air flows into the lungs at any given pressure difference between the atmosphere and alveoli.
The major determinant of airway resistance is__
the radii of the airways
The surface area of alveoli is ____
how much volume approx?
80m2
Fits a volume of approx 6L (3L in each lung)
What is ventilation?
The bulk flow of air in the lungs and bulk flow of air out of lungs
Does not tell us anything whether that gas or 02 is getting into the blood or co2 can get out of the blood.
What is pulmonary ventilation?
total air movement into/ out of the lungs (relatively insignificant in functional terms)
(L/min)
what is alveolar ventilation
fresh air getting to the alveoli and therefore available for gas exchange (functionally more significant)
(L/min)
How to tcalculate pulmonary volume?
tidal volume x respiration rate?
calculate alveolar difference
tidal volume - dead space vol x respiration
= ___(L/min)
Partial pressure
Daltol’s Law - total pressure gas micture is sumof pressure of the individual gases.
air = 79% nitrogen and 21% o2. negligible co2 (0.03%)
if patient has ^ c02 is that from breathing too much Co2?
no.
it’s due to a pathology which is preventing exhaling out the co2. We are the producers of co2
Define partial pressure
The pressure of a gas in a mixture of gases is equivalent to the % of a particular gas in the entire mixture multiplied by the pressure of the whole gaseous mix.
e.g. atmospheric P = 760mmHg
pressure of are we breath therefore = 760mmHg
21% air we breathy = o2
partial pressure of o2 in aie = 21%x760mmHg = 160 mmHg
what is our normal alveolar ventilation?
4.2L/min
Why is partial pressure less through alveolar ventilation than calculated?
160,,Hg - in graph 100,,Hg -
Air we breathe is diluted by 2 things - anatomical dead space and tidal volume breathed in are only 70% efficient and the air is diluted (saturates) with water vapour.
and pressure of gas equilibrium,
what happens with alveolar ventilation during hypoventilation
reduction of ventilation due to less air getting to the alveoli for gas exchange
o2 levels in alveoli fail as taken away bu blood + metabolised by peripheral tissue faster than being replenished by alveoli
co2 levels increase faster than able to breathe out = co2 levels rise and seen in blood. > partial pressure of oc2 rise pressure drops of o2 drop
What happens to alveolar ventilation in hyperventilation
Increased alveolar ventilation - pressure of o2 rises and oressure of co2 falls
What levels are our primary driving force for breathing?
co2 levels
what is alveolar ventilation significantly influenced by?
Dead space
which type of ventilation is functionally more important
Alveolar ventilation MORE important than pulmonary ventilation
what is more influential in determining alveolar ventilation? rate or depth
depth of breathing of more influential than determining alveolar ventilation than the rate of breathing
because of the effect of anatomical deadspace
in what direction does alveolar ventilation decline and why
with height from base to the apex of an upright lung due to changes in compliance.
what is normal alveolar partial pressure or 02?
normal alveolar partial pressure (asnd therefore systemic arterial PP) of 02 is 100mmHg (13.3 kPa)
what is the normal Alveolar partial pressure of co2?
Normal partial prssure ~(and therefore systemic arterial PP) of co2 is 40mmHg (5.3 kPa)
The pulmonary artery carries
deoxygenated blood AWAY from the heart to the lungs
The Pulmonary vein carries
oxygenated blood TOWARDS the heart from the lungs
Pulmonary circulation ____
Is opposite from systemic circulation in the function it delivers co2 to the lungs and picks up o2 from air.
BRONCHIAL CIRCULATION___
nutritive supplies via bronchial arteries from systemic circulation to supply oxygenated blood to lung tissues. complises 2%of left heart output. blood drains to left atrium via pulmonary veins
Pulmonary circulation (gas exchange)
consists of l+ R pulmonary arteries originating from right ventricles. entire cardiac output from right ventricle. supplies dense capillary network surrounding the alveoli and returns oxygenated blood to the left arrrium via pulmonary vein high flow, low pressure system (25/100mmHg pulmonary vs 120/80mmHg systemic)
systemic artery partial pressure reflects what is happening in ____
the alveoli,
systemic venous blood reflects what is happening in
our peripheral tissues.
where does systemic venous blood go back to
the right side of the heart.
Appreviations
A -
a -
V
A - alveolar
a - arterial blood
V - mixed venous blood (e.g. in pulmonary artery)
What is Pao2
Partial pressure of oxygen in artierial blood
What is PAco2
Partial pressure of co2 in alveolar air
with gas exchange, how is the rate of diffusion proportional
- directly proportional to the pressure gradient
- directly proportional to gas solubility
directly proportional to the available surface area
- inversely proportional to the thickness of the membrane
- most rapid over short distances
describe why solubility is important for diffusion rate
co2 is very soluble in water o2 is not very soluble the faster it will be if more soluble.
PP o2 100 mmHg - 46mmHg
co2 40mmHm - 46mmHg
so PP would say 02 is faster BUT solubility c02 is more so would be faster - this is why the rate is relatively the same as these 2 factors make the rate similar.
where do the elastic fibres on alveoli never sit
between a blood capillary and the alveoli = less distance for diffusion to occur.
diffusion of gases between the alveoli and the blood obey rules of ___
simple diffusion
__ diffuses more rapidly because of its ___
however, the overarall rate of ____ between ___ and ___ are similar because of the ______ for ___
co2 diffuses more rapidly because of its greater solubility. however, the overall rate of equilibrium between o2 and co2 are similar because of the greater pressure gradient for o2
The anatomy of the lung is optimally adapted to maximise gas exchange because of ___:
- larger surface area, minimum diffusion distance, thin cell membranes (type 1 alveolar cell capillary cell)/
what impact does emphysema have on gas exchange
destruction of alveoli reduces surface area for gas exchange
what impact does fibrosis have on gas exchange
thickened alveolar membrane slows gas exchange. loss of lung compliance may decrease alveolar ventilation
what impact does pulmonary edema have on gas exchange
fluid in interstitial space increases diffusion distance
material pco2 may be normal due to higher co2 solubility in water (increase diffusion distance po2 low)
what impact does asthma have on gas exchange
increased airway resistance decreases airway ventilation
in fibrosis what can you see a difference in through histology
normal alveoli, blood cells and some connective tissue
in fibrosis presence fibrotic tissue.
fibrosis in lung xray
fibrosis is opaque you can see
emphysema lung
emphysema break down the alveolar membrane and loss of elasticity. loss surface areas for gas exchange
main cause for emphysema
smoking
what muscles are people with emphysema having to use for breathing?
use muscles of expiration - internal intercostal muscles to pull ribcage down and in
use abdominal muscles to push their abdominal contents up into the diaphragm - push the diaphragm up into thoracic cavity and increase the pressure to force air out.
what happens with compliance in fibrosis and emphysema
fibrosis - compliance decreases because fibrous tissue resists the stretch.
emphysema - lose elasticity because of breakdown elastic fibres - compliance increases due to lost resistance.
what does oedema do to compliance?
no effect in compliance - no effect ventilation but increased diffusion distance means harder for gases to (particularly o2) diffuse so impacted partial pressure.
what effect foes asthma have on diffusion
little effect on diffusion and a mainly big effect on ventilation end up having an impact on the partial pressure of o2 and co2 in alveoli
= reduces pp of 02 and increase pp of co2.
emphysema causes ____
loss of surface area
fibrosis causes _____
increased thickness of membrane
oedema cauaes___
increased diffusion distance
what is an obstructive lung disease
obstruction of airflow especially on expiration
explain restrictive lung diseases
restriction of lung expansion
Conditions that are obstructive lung diseases
Asthma
copd
chronic bronchitis
emphysema
Restrictive lung diseases:
Restriction of lung expansion + loss of xompliance
Fibrosis
asbestosis
infant respiratory distress syndrome
oedema
pneumothorax
what is spirometry
the technique used to measure lung function can be static or dynamic
static where only consideration volume exhaled
dynamic time taken to exhale certain vol is what is measured
what levels can spirometry measure
tidal vol
inspiratory vol
inspiratory capacity
expiratory reserve vol
vital capacity
what levels can spirometry NOT measure
Total lung capacity
functional residual capacity.
residual volume
common lung function tests
FEV1/FVC
forces expiratory volume in 1 second
what is a normal volume in FEV1
fir healthy adult 4.0L
what is a normal FVC
normal fit health is 5.0L
what is normal % of fev1/fvc
80%
In disease what would fev1, fvc and ratio be in
normal
fev1 = 4.0L
fvc = 5.0L
% = 80
In disease what would fev1, fvc and ratio be in
obstructive disease
fev1= 1.3
fvc = 3.1L
% = 42
In disease what would fev1, fvc and ratio be in
restrictive lung disease
fev1 = 2.8
fvc = 3.1
% = 90
explain fev1 fvc levels in obstructive condition
the rate at air exhales is slower
total expired volume (fvc) is reduced (FRC functional residual capacity may be increased)
the major effect is on the airway so fev1 is reduced to a greater extent than FVC
ratio reduced
explain fev1 fvc levels in restrictive condition
- absolute rate of airflow reduces (due to total lung vol reduced)
- total volume reduced due to limitation to lung expansion
- ratio remains constant or can increase as a large proportion of volume can be exhaled in the first second.
obstructive lung diseases increase work of
expiration
Restrictive lung diseases increase the work of
inspiration
Distribution of blood flow in lungs
Both blood flow and ventilation decrease with height across the lungs
less ventilation and perfusion in the apex of the lung.
where is the lung does blood flow or arterial pressure exceeds each other
the base of the lungs blood flow exceeds alveolar pressure, this compresses the alveoli.
where are the perfusion ventilation mismatches and what are they? where is precisely matched?
the apex is mismatched with ventilation exceeding blood flow
the base of the lung is mismatched with blood flow exceeding ventilation
the 3rd rib is where the ventilation-perfusion balance is equal.
where is the biggest ventilation-perfusion mismatch?
apex
what are the ratios of ventilation-perfusion mismatch?
perfectly matched ventilationperfusion ratio = 1.0
mismatch 1 (base) = <1.0
mismatch 2 (apex) ventilation > perfusion >1.0
what is shunt
blood is moved from right side of the heart to the left without gas exchange
what happens to blood when it is in an area of the lung that is poorly ventilated? (hypoxia)
smooth muscle in the area restrict blood to that area by constricting in response to hypoxia. shunt
perfusion greater than ventilation
alveolar po2 falls = pulmonary constriction
pco2 rises = bronchial dilation
what is the systemic circulation response to an area of hypoxia?
tissue dilates to allow more o2 to travel to the area
what is alveolar dead space?
when ventilation exceeds blood flow.
opposite of shunt.
what happens (mismatch) with pulmonary embolism?
ventilation exceeds blood flow. embolism impedes blood flow = alveolar deadspace.
increase 02 and decrease co2
alveolar po2 rises = pulmonary dilation
pco2 falls - bronchiconstirction
What is physiological dead space
alveolar dead space + anatomical deadspace
Pulmonary arterial pressure is ___ the systolic p ___ diastolic p ___.The ____ pressure circuit susceptible to the effects of ___ and this gives rise to the degree of variability. The ___ of the lung is highly perfused compared with the ___ of the lung
Pulmonary arterial pressure is low: systolic p - 25mmHg diastolic p -8mmHg .The low-pressure circuit susceptible to the effects of gravity and this gives rise to the degree of variability. The base of the lung is highly perfused compared with the apex of the lung
ventilation varies with ___. and is greatest at the ___. This ventilation is due to changes in the ___ across the lung. The ventilation-perfusion ratio ___ from ___ to__ in the upright lung. This inequality is compensated by ___ of ___ controlled by ___
ventilation varies with height. and is greatest at the base. This ventilation is due to changes in the compliance across the lung. The ventilation-perfusion ratio increases from the base to apex in the upright lung. This inequality is compensated by local regulation of blood flow controlled by local po2
what describes alveoli that are perfused but underventilated
shunt
what described alveoli that are ventilated but under perfused
alveolar deadspace
alveolar deadspace (normally small) + anatomical deadspace
physiological deadspace
what is respiratory sinus arrhythmia
acts to minimise ventilation-perfusion mismatch during the breath cycle.
how much is the demand of 02 to resting tissues
250 ml/min
arterial 02 content (plasma)
3ml/L
how much 02 can haemoglobin carry?
197ml of 02/l
how much % of arterial 02 id extracted by peripheral tissues at rest?
25%
when referring to the partial pressure of oxygen in the blood: what are we referring to
we are only referring to the amount of o2 in plasma, NOT referring t how much o2 is wrapped up in haemoglobin
the amount of o2 in the solution in plasma is determined by__
the partial pressure of o2 that is in our alveoli
the partial pressure of o2 in the alveoli is determined by
our alveolar pressure
what is the normal partial pressure of resting tissues?
how saturated is haemoglobin at this stage?
40mmHg
75% saturdates Hb
in anaemia describe
anaemia is defined as a condition where the o2 carrying capacity of blood is compromised (iron deficiency, haemorrhage, vitb12 deficiency)
what would happen to the partial pressure of o2 in anaemia
The partial pressure of o2 is normal. total blood o2 is compromised.
the amount of o2 in solution is partial pressure - determined by partial pressure o2 in alveoli.
if normal lung function - normal ventilation - normal diffusion. normal partial pressure o2 in plasma.
LOSS of blood cells or making not enough means no place to store o2
can you have a low partial pressure of o2 and normal total blood o2 content?
no. because the partial pressure of o2 determines how mich o2 binds to haemoglobin.
if pp falls - o2 content also falls.
can you have low o2 content but normal partial pressure of o2?
the amount of o2 in solution is partial pressure - determined by partial pressure o2 in alveoli.
if normal lung function - normal ventilation - normal diffusion. normal partial pressure o2 in plasma.
LOSS of blood cells or making not enough means no place to store o2 so low o2 content but normal partial pressure
can red blood cells be fully saturated in anaemia?
yes can be fully saturated - what determines the saturation of haemoglobin is the partial pressure of o2. (normal) so saturation can occur
what factors change affinity of haemoglobin for oxygen?
PH
Pco2 (partial pressure co2)
Temp
DPG (diphosphoglycerate) 2,3
what happens if there is an increase in factors that determine haemoglobin affinity for 02
(temp, ph, pco2)
the affinity for o2 drops releasing more 02
what happens if there is an decrease in factors that determine haemoglobin affinity for 02
(temp, ph, pco2)
affinity rises and releases less o2.
what happens to the affinity of haemoglobin to o2 in hypothermia
the affinity is high still, holing on to o2 and not giving to peripheral tissues
what is dpg2,3
is a by-product of red blood cell metabolism.
where or when is dpg 2,3 produced?
in situations and regions where there os less o2 available.. in states of hypoxia.
may be in chronic lung disease or chronic heart disease
explain carbon monoxide exposure and haemoglobin affinity
co binds to haemoglobin 250x more affinity than 02 and slowly dissociates. pc0 of only 0.4mmHg causes progressive carboxyhaemoglibin formation
characterised by hypoxia, anaemia, headache, cherry red sckin and mucous membranes.
resp rate usually unaffected due to normal arterial Pcp2. leads to potential brain damage and death.
treatment involved providing 100% o2 to increase Pao2
what is the difference between partial pressure and gas content?
arterial partial pressure (Pao2) is not the same as arterial o2 concentrations.
pao2 refers purely to o2 in solution in plasma and determined by o2 solubility and the partial pressure of o2 in the gaseous phase that is driving o2 into solution.
partial pressure is not the same as concentration as varies depending on the form the molecules are in. (e.g. 30x more o2 in 1L gas than 1L in plasma)
EXPLAIN air embolism and what this means with gases travelling in plasma
gases are travelling around the body NOT in a gaseous phase but in a solution
air embolism is bubbles in the blood where gases are in their gaseous phase travelling in plasma.
each litre of systemic arterial blood contains ___ml of o2.
more than __% bound to haemoglobin. the rest is dissolved in ____
Haemoglibin cooperatively binds to __ molecules of o2.
____ml p2 binding to each gram of haemoblibin.
The reaction of o2 binding and releasing from haemoglobin is a ___ reaction not a __ reaction
each litre of systemic arterial blood contains -200ml of o2.
more than 98% bound to haemoglobin. the rest is dissolved in plasma
Haemoglobin cooperatively binds to 4 molecules of o2.
1.34ml o2 binding to each gram of haemoglobin.
The reaction of o2 binding and releasing from haemoglobin is an oxygenation reaction not a oxidation reaction
name 5 haemoglobin types
Haemoglobin A. This is the most common type of haemoglobin found normally in adults.
Haemoglobin F (fetal haemoglobin). This type is normally found in fetuses and newborn
Hemoglobin A2. This is a normal type of haemoglobin found in small amounts in adults.
Glycosylated haemoglobin - HbA1a, HbA1b, and HbA1c is a form of haemoglobin (Hb) that is chemically linked to sugar.
what is another oxygen-carrying molecule and where would you usually find it?
when would you find it elsewhere I n the body?
Myoglobin
usually found in cardiac and skeletal muscle
you would only usually find in circulation if you have extensive muscle damage
explain main types of hypoxia
1. hypoxaemic hypoxia - most common - reduces o2 diffusion in lungs due to reduces po2 atmosphere or tissue pathology
2. anaemic hypoxia - reduces o2 carrying capacity due to anaemia, reb loss/ iron deficiency
3. stagnant hypoxia - heard disease inefficient pumping of blood to lungs/around body
4 histotoxic hypoxia - poisoning prevents cells utilising o2 delivered to them e.g. co poisoning/cyanide
5 metabolic hypoxia o2 delivery to tissue doesn’t meet increased demand by cells
the partial pressure of the o2 in blood and o2 concentration in the blood is the same things
true or false?
false. not the same thing
partial pressure describes what in relation to ___
and not ____
partial pressure which described amount of o2 in solution in the plasma, not total o2 content in the blood
does partial pressure determine o2 content in blood?
yes partial pressure determines total o2 content of blood by determining saturation of haemoglobin, where 98% of o2 in blood is carried
what has higher affinity HbF or HbA1
Haemoglobin HbF (foetal haemoglobin) has a higher affinity for hba1 (adult haemoglobin) to allow them to extract o2 from the maternal systemic circulation that they would otherwise not have access to.
ventilatory Control requires the stimulation of ____ of ___
skeletal muscle of inspiration
What stimulates the muscles of inspiration?
The phrenic nerve (to the diaphragm) and intercostal nerves (to external intercostal muscles)
at rest, expiration is _____ so ____ is required
at rest, expiration is passive so no neural input is required
Ventilatory control what area of spinal cord the origin would breathing cease if severed?
breathing dependent on signalling from the brain (sever cord above the origin of the phrenic nerve c3-5 and breathing ceases
how is respiratory rhythm modulated by Respiratory centres
- emotional (via limbic system in the brain) (anxious, crying)
- voluntary override (viahigher centres in the brain)
- mechano-sensory (stretch receptors) input from the thorax - stretch reflex
- Chemical composition of the blood )pco2, po2 and ph) detected by chemoreceptors
why do we expire in a smooth controlled manner?
use of basal tone in our muscles of expiration. we are not actively causing them to contract - basal tone is slow controlled and smooth. no need to contract we are not forcing air out during expiration at rest
dordal respiratory group switches off and stops inspiratory muscle contraction. relax to starting position
where are chemoreceptors for breathing`
central and peripheral chemoreceptors
explain chemoreceptors for breathing
central chemoreceptors: medulla - respond directly to h+ which directly reflects pco2 primary ventilatory drive.
Peripheral chemoreceptors: carotic and aortic bodies
respond primarily to po2 (less pco2) and plasma h+
secondary ventilatory drive
central chemoreceptors
detect changed in [H+] in csf around brain
causes reflex stimulation of ventilation folliowing rise in [h+] deiven by raised pco2 (hyper capnia)
co2 +h2o h2co3 >-< h+ + hco3-
what happens with ventilation with chemoreceptors if there is a decrease in h+
ventilation is reflexible inhibited by a decrease in arterial pco1 (reduces csf [h+] = hyperventilation you will stop breathing for a short time because expired all c02
do not respond to direct change in h+
why can central chemoreceptors not respond directly to hydrogen ions in plasma
they are reflecting levels of co2 in blood the negative feedback loop ensures normal pco2
they cannot respond to hydrogen ions in the plasma because those ions do not cross the blood-brain barrier.
what happens with build-up of pco2
if we increase pco2 we double ventilation body sensitivity to pco2
chronic lung disease explain for ventilation
chronically exposed to co2 levels and desensitised.
they rely on peripheral chemoreceptors rely in pao2 - driven by hypoxia.
peripheral chemoreceptors
carotic artery and aortic body
detect changed in arterial po2 and h+ pao2
cause reflex stimulation of ventilation following significant fall in po2
(below >60mmHg)
- consider harmoglobin dissosiation curve
what will happen to respiration rate in an anaemic patient with normal lung function, who has a blood oxygen content half the normal value?
- increase
- decrease
- stay the same
it will stay the same
because lungs are working normally. diffusion take place normal peripheral response to partial pressure o2 and NOT total o2 content. PAO2 NORMAL.
AS PAO2 IS WHAT PERIPHERAL RECEPTOR MONITOR NO INCREASE IN RESP RATE. ASSING MORE O2 WOULD DO LITTLE BECAUSE RBC is already saturated 98%. there are not enough RBC
explain sedation/anaesthesia and ventilatory control
most gaseous anaesthetic agents increase resp rate but decrease tidal volume (tidal vol is the main determinant of alveolar ventilation)
what effect do barbituates/opioids have to respiratory centes?
barbiturates and opioids depress resp centres. overdose results in death due to resp failure. decrease in sensitivity to PH and response to pco2. also, decrease peripheral chemoreceptor response reduced po2.
explain nitrous oxide to chemoreceptor response
a common sedative/light anaesthetic agent blunts peripheral chemoreceptor response to falling pa02. Very safe in most individuals but problematic in chronic lung disease cases where individuals are on hypoxic drive. Administering o2 to these patients aggravates the situation
remember most people work on central chemoreceptors - hypoxic driven work in levels in peripheral chemoreceptors
explain why nitrous oxide is not good for patients with chronic lung disease
this blunts the peripheral chemoreceptor to pao2 levels dropping. The central chemoreceptors are already lost due to chronic exposure to co2. giving nitrous oxide blunts the peripheral chemoreceptors - patient now has no means of regulating blood gas composition. co2 levels dramatically rise o2 levels drop and the body cannot respond because insensitive - this is dangerous
co2 = toxic - o2 drop cannot supply to the brain - function disrupted.
** giving o2 - co2 is still built up and holds on in the body - the excess 02 stops them from breathing
The main factor determining ventilation is
the chemical composition of the plasma
the strongest factor influencing ventilation is
the partial pressure of co2 in the plasma paco2
what play a secondary role in ventilation
paco2 and plasma ph play a secondary role
what play a dominant role in ventilatory control
central chemireceptors
what play a more minor role in ventilatory control in healthy individuals
peripheral chemoreceptors
what impact can low total blood oxygen content have on ventilation
low total blood content (anaemia) will have little impact on ventilation if pao2 (o2 in solution in plasma) is normal
what effect do all sedetive or anaesthetic drugs have on ventilation
will depress ventilation to some degree
peripheral and central chemoreceptors responding to h+
An increase in co2 increases hydrogen ion concentration in the plasma as well as in the cerebrospinal fluid
central chemoreceptors cannot respond to h+ ions that are not from co2 in the plasma because they cannot cross the blood-brain barrier.
peripheral chemoreceptors will respond to h+ ions whatever source they have originated from
the following will be the strongest stimulus to ventilation:
- PO2 80mmHg
- PCO2 44mmHg
- PCO2 38mmHg
- Plasma pH7.3
- Plasma pH7.6
Small increases in PCO2 are all that is required to strongly stimulate ventilation. Large decreases in PO2 are required to do the same thing <60mmHg. Decreases in PCO2 and increases in pH will both slow down ventilation.
Which of the following will stimulate ventilation?
- Acidosis (pH<7.4)
- PCO2 44mmHg
- PO2 60mmHg
- All of the above will stimulate ventilation
All those factors will stimulate ventilation (the fall in PO2 is great enough this time to trigger the peripheral chemoreceptors)
What does hypoventilation cause?
Hypoventilation means breathing less than normal, i.e. having alveolar ventilation less than the normal value of 4.2L/min. This reduction in breathing means CO2 is retained (not exhaled so readily), and when CO2 levels rise the CO2 is converted into carbonic acid thus raising [H+] and creating acidosis. Exceeding normal alveolar ventilation (4.2L/min) is hyperventilation. Alveolar ventilation could fall below 5L/min (but not below 4.2L/Min) and still be greater than normal.
What is the normal ph of extracellular fluid?
7.4 ph
what happens to which receptors in exercise
the body produces lactic acid. the peripheral chemoreceptors will respond to the production of lactic acid in a way central chemoceptors cannot because they cannot cross the blood-brian barrier
what will alter ventilation a change in ___ and what pathway will do this
changes in plasma ph will alter ventilation via the peripheral chemoreceptor pathway
if plasma PH falls___
if plasma ph falls, h+ contentration increases and ventilation will be stimulated due to acidosis.
if plasma ph rises__
plasma ph rises (h+) falls (e.g. vomiting) alkalosis will occur and ventilation will be inhibited.
Increased ventilation will drive the equation to the ___
decreased ventilation drives the equation to the __
increased ventilation drives the equation to the left (by blowing off co2 and lowers h+)
decreased ventilation drives this equation to the right (by retaining co2 and increasing h+)
briefly explain the acid-base balance with respiratory and another system
the acid-base balance of the respiratory system, the renal system will work together to try and maintain normal extracellular ph.
if renal has =acid base imbalance, the respiratory will try and compensate to correct it
acid-base balance, hypoventilation and hyperventilation
hypoventilation causing co2 retention leads to increased h+ and brings about respiratory acidosis
hyperventilation, blowing off more co2 leads to decreased h+ bringing about respiratory alkalosis.
if the respiratory system is not the cause of a ph disturbance it is called….
metabolic acidosis or metabolic alkalosis - the respiratory system can try and compensate for that and acts to limit damage and reduce the amount of h+ ion concentration.
what is normal value of ph
7.4
useful ph equation
ph a hco3/co2
hco3 is controlled by the kidneys
co2 is controlled by the lungs
what happens with ventilation during breath holding
we will eventually lose consciousness and lose the ability to control ventilation and involuntary start normal ventilation
]what happens with ventilation during intended hyperventilation
ventilation is reflexible inhibited by an increase in arterial po2 or a decrease in arterial pco2/[h+]
respiration and swallowing
respiration is inhibited during the swallowing period to avoid aspiration of food or fluid,
swallowing is followed by expiration to dislodge any particles that may be dislodged outwards from the region of the glottis
changes in plasma [h+] are detected by __
peripheral chemoreceptors
increasing [h+] in plasma stimulates
ventilation
decreasing h+ in plasma ___
depresses ventilation
PLasma h+ ogten but not always originated from ___
co2 so the increase in ventilation helps to bloww off that co2
changes in plasma h+
will alter ventilation
Changes in ventilation will __
alter plasma [h+]
The respiratory system can therefore be either ____ or ____ for ____
the respiratory system can therefore be either the cause of or compensate for acid base disturbences
a key equation to remember is ___
ph is proportional to bicarbonate divided by co2
ph a hco3/co2
our bodies are wholly programmed to ___ when it cannot it causes __
our bodies are wholly programmed to get rid of co2, when they cannot it causes immense distress
while some ___ is possible, it cannot ___the ___.
while some voluntary control is possible, it cannot overrride the chemical control mechanisms.
The functional unit of the lung is the pulmonary alveolus.
true or false
True. The alveoli are the only point of the respiratory tree where the walls are thin enough to allow gas exchange, and hence they are the only point where functional gas exchange occurs.
The correct answer is ‘True’.
Regarding airways and breathing: Vital capacity is the same as Inspiratory Reserve Volume + Functional Residual Capacity.
true or false
False. Vital capacity describes the largest volume of air that can voluntarily be exhaled after a maximum inspiration. IRV + FRC misses out tidal volume. Vital capacity can be alternatively described in a number of ways:
- Inspiratory Capacity + Functional Residual Capacity
- Inspiratory Reserve Volume + Tidal Volume + Functional Residual Capacity
- Inspiratory Reserve Volume + Tidal Volume + Expiratory Reserve Volume + Residual Volume
Remember, the term “Capacity” describes where 2 or more “volumes” have been added together.
The correct answer is ‘False’.
Alveolar ventilation is defined as the total volume of gas breathed per minute.
true or false
false
Alveolar ventilation describes only the volume of gas that reaches the alveoli (and hence is available for gas exchange) per minute. Not all the air we breathe in reaches the alveoli as some gets trapped in dead space and cannot participate in gas exchange.
The correct answer is ‘False’.
Regarding airways and breathing: If there are ventilation/perfusion disturbances, the impact is greater on CO2 loss than O2 uptake
true or false
False. CO2 is more water-soluble than O2 so can diffuse more readily. For this reason, ventilation/perfusion disturbances often affect CO2 levels less than O2.
The correct answer is ‘False’.
Carbon dioxide is carried on the haemoglobin molecule as carboxyhaemoglobin.
Select one:
True
False
False. The term “carboxyhaemoglobin” describes carbon monoxide binding to haemoglobin – your carboxyhaemoglobin levels should be neglible!
The correct answer is ‘False’.
The volume of blood flowing through the pulmonary circulation per minute is less than in the systemic circulation.
Select one:
True
False
False. The two systems are in series with each other so the same volume of blood must flow through each for any given period of time.
The correct answer is ‘False’.
The total volume of both lungs is called the vital capacity.
Select one:
True
False
False. The total volume of both lungs is Total Lung Volume. Vital capacity describes the maximum volume of air that can be exhaled following a maximum inspiration.
The correct answer is ‘False’.
The phrenic nerve takes its origin from the T3, T4 and T5 spinal nerves.
Select one:
True
False
False. The phrenic nerve takes it origins from the C4, C4 and C5 spinal nerves
The correct answer is ‘False’.
The haemoglobin-O2 saturation curve is moved to the left by a rise in pH.
Select one:
True
False
True. Alkalosis increases the affinity of haemoglobin for oxygen and thus shifts the binding curve to the left
The correct answer is ‘True’.
Central chemoreceptors respond to changes in H+ concentration.
Select one:
True
False
True. Specifically, they respond to changes in H+ concentration in the cerebrospinal fluid (CSF). These H+ are wholly derived from CO2 present in the CSF, which in turn is in equilibrium with CO2 in the plasma so indirectly the central chemoreceptors are responding to increases in CO2 in the plasma. H+ from other metabolic sources cannot cross the blood-brain barrier and so do not stimulate the central chemoreceptors
The correct answer is ‘True’.
The term shunt describes the passage of blood through the lungs where the opportunity for gas exchange does not occur.
Select one:
True
False
True. Shunt describes the situation where blood is effectively “shunted” from one side of the heart to the other without participating in gas exchange in between. It can happen where part of the lung is not being fully ventilated for some reason e.g. tumour, airway obstruction
The correct answer is ‘True’.
The haemoglobin-O2 saturation curve will be shifted downward in an anaemia with normal lung function.
Select one:
True
False
False. The oxyhaemglobin binding curve is unaffected in anaemia. In anaemia the amount of oxygen in solution in the plasma is unaffected (providing the lungs are healthy) and therefore the binding of oxygen to red blood cells is normal. The term anaemia describes a fall in the total oxygen content of the blood but remember 98% of the oxygen in the blood is wrapped up in the haemoglobin in red blood cells, it is not in solution in the plasma. If the lungs are working normally, anaemia therefore comes about due to diminished ability of red blood cells as a whole to carry oxygen for one reason or another e.g. lacking in number, or in oxygen binding sites due to iron deficiency. However the red blood cells that are present in the blood are fully saturated at normal PO2, even if they have fewer binding sites than normal.
The peripheral chemoreceptors in the carotid bodies are more influenced by arterial PO2 than by arterial oxygen content.
Select one:
True
False
True. The peripheral chemoreceptors respond to changes in levels of oxygen in solution (PO2) and not the amount of oxygen wrapped up in hemoglobin (where most of the blood oxygen in found).
Peripheral chemoreceptors mediate the hypocapnia (low PCO2) that occurs at high altitude.
Select one:
True
False
True. The lower atmospheric PO2 at altitude means arterial PO2 also falls. This is detected by the peripheral chemoreceptors which stimulate ventilation in an attempt to restore normal PO2. The resulting hyperventilation blows of more CO2 than normal leading to hypocapnia.
